Electrolytic refining of copper



'ilt'ur'rnn' Sterne KEEN? 53mins,

ELIAS A. SMITH, o F ANACONDA, MONT-ANA.

ELECTROLYTIC REFINING GF GQPPER.

SPECIFICATICH forming part of Letters Patent Nmfi EQfiSB, dated January 17, 1899.

Application filed May 19. 1898. seen Ila. 681,129. on specimens.)

To all whom it 12mg concern.-

lle it known that I, ELIAS .A. SMITH, a resident of Anaconda, Deer Lodge county, Montana, have invented certain new and useful Improvements in the Electrolytic Refining of Copper, of which the following is hereby declared to be a full,clear,and exact description. In the electrolytic'method of refining copper .by immersion of copper anodes in a suitable bath of acid electrolyte the impurities associated with the copper in the anodes and which are composed mainly of iron, arsenic, and antimony become affected electrochemically and by virtue of the reactions pass in part into solution and in part are thrown down to settle with the slinies. Such of the impurities as remain in solution tend-in measure to deposit with the copperor are apt otherwise to allect inj uriously the quality of the copper yield. Since these impurities are being continuously supplied from the anodes, the gradual accumulation of the objectionable ingredients su dices to compel a periodic renewal of the electrolyte solution. In most refineries the practice now is to evaporate the impure electrolyte, and thus to recover the bulk of the copper salts, (blue vitriol.) The blue vitriol crystallizes out of the cool concentrated solution and being redissolved is restored again to the refinery bath, whereas the mother-liquor which still retainsthe impurities is generally rejected and allowed to run to waste. The invention aims to utilize this refuse mother -liquor by regenerating it for restoration to the electrolyte substantially as follows: After removal of the bulk of the copper salts (blue vitriol) by aid of a regular crystallizin g plant the solution which reniains 'i. 0., the refuse mother-liquor-is further evaporated. A system of lead pans, such as is commonly used for concentrating sulfuric acid, can be conveniently employed 1" or the purpose. Du ring this secondary evapodically removethe precipitatcdiron salts.

The impure mother liquor should be com tinually fed in usual manner to advance progressively along the system of evaporating- 5 5;

pans, as well understood. Eventually-the concentrated acid there contained may reach a strength somewhere about 55 Baume.

' Emerging from the pans the acid runs through a set of water-jacketed cooling-tanks, thence along troughs for settling, and ultimately discharges into big precipitating-vats. U nder quiet clarification the remnants of copper sulfate, if any, and some part of the ammo- I niumsulfate, if this be present in the original electrolyte, will crystallize out. To the clear and concentrated acid yet remaining and left quite cool, comparatively, within the tank are now addedcrystals of sodic or calcichypo- H s fi 'e..-, l?hese additionsare .HIQQLEQlQdHlLKQ stirred in and efiect the precipitation of the antimony and arsenic. furous acid is also liberated, but ewing to the cool temperature of the sulfuric-acid bath the liberated supply remains intimately'blended or dissolved in such bath. Typical examples of the two sorts of reaction may be stated-by equationsihus:

The equations show that the hyposulfite crystals react in part directly with the sulfuric .85

to generate nascent sulfur, which latter'etfects precipitation of the arsenic and antimony. On dilution the arsenic and antimony com- 0 pounds resulting from the treatment proceed to settle away. A minor portion of the sulfur also separates out, leaving the sulfuric acid clarified and regenerated, free from all impurities and in readiness to be restored anew to the electrolyte bath at the refinery. By allowing the concentrated sulfuric acid to cool down before adding the crystals of hyposulfite the precipitation of the arsenic and an timony is more certainly accomplished. Be

sides, except for such cool state, the retention of the liberated sulfurous acid could not other: wise be assured; The free sulfurous acid thus dissolved as an incident of the regpner- A supply of free sulation treatment has a tendcncyto reduce the electrolyte. llence at the refinery it prevents the arsenic from passing into solution as arscnate of copper, the almost insoluble arscnous acid which forms being retained as such, and thus being compelled to settle down with the silver slilnes. The free sulfurous acid also tends toreduce ferric to ferrous sulfate. The latter salt requires a higher tension current for decomposition than is requisite for copper sulfate. Hence under the reducing influence of the sulfurous acid less iron deposits on the cathode along with the copper than would occur were this reducing agent absent from the bath.

Obviously the details can be'varied according to the mechanics skill without departure from the essentials of the improvement.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is- V l. The electrolytic method of refining coper-which consists in depositing thecopper rom anodes thereof immersed in an acid-bath, concentrating the resultant impure electrolyte to recover by crystallization the bulk' of the copper salts (blue vitriol), further-treatin g the mother-liquor by progressive shallow evaporation at high temperature, under air exposurato throw downtime iron salts and to'gradually concentrate the free acid; and upon subsequent cooling th en adding suitable hyposulfite to remove the antimony and ar from anodes thereof immersed in an acid-bath,

concentratii'ig the resultant impure electrolyte to recover by crystallization the bulk of the copper salts (blue vitriol), further treating 45 the mother-liquor by progressive shallow evaporation at high temperature, under air exposure, to throw down the iron salts and to gradually concentrate the free acid, and

upon subsequent cooling then adding suitable hyposulfite to remove the antimony and arsenic while retaining liberatedsulfurousacid in solution, so that the same may serve as a reducing agent on return of the regenerated acid to the refinery-bath substantially as de scribed. a v ELIAS AfsMrru.

\Vitnesses: v r

'lnos. F. TOOMEY,

JOHN C. SALOR. 

